[PATCH] D103435: [PoC][RISCV] Define a symbol flags and a dynamic tag to avoid lazy binding for vector calls.

[Hsiangkai Wang via Phabricator via llvm-commits]

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This is the primitive work for https://github.com/riscv/riscv-elf-psabi-doc/pull/190.

Functions with vector arguments will use vector registers to pass
arguments, In the dynamic linker resolver, we plan not to save/restore
the vector argument registers for lazy binding efficiency. To avoid
ruining the vector arguments by the dynamic linker resolver, functions
with vector arguments will not go through the resolver.

To achieve the goal, we will annotate the function symbols with
STO_RISCV_VARIANT_CC flag and add DT_RISCV_VARIANT_CC tag in the dynamic
section. For assembler, we add a new directive, .variant_cc, to annotate
the symbol has special calling convention and does not go through the
resolver.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D103435

Files:
  llvm/include/llvm/BinaryFormat/DynamicTags.def
  llvm/include/llvm/BinaryFormat/ELF.h
  llvm/lib/Object/ELF.cpp
  llvm/lib/ObjectYAML/ELFYAML.cpp
  llvm/lib/Target/RISCV/AsmParser/RISCVAsmParser.cpp
  llvm/lib/Target/RISCV/MCTargetDesc/RISCVELFStreamer.cpp
  llvm/lib/Target/RISCV/MCTargetDesc/RISCVELFStreamer.h
  llvm/lib/Target/RISCV/MCTargetDesc/RISCVTargetStreamer.cpp
  llvm/lib/Target/RISCV/MCTargetDesc/RISCVTargetStreamer.h
  llvm/lib/Target/RISCV/RISCVAsmPrinter.cpp
  llvm/lib/Target/RISCV/RISCVRegisterInfo.cpp
  llvm/lib/Target/RISCV/RISCVRegisterInfo.h
  llvm/test/CodeGen/RISCV/rvv/fixed-vectors-variant-cc.ll
  llvm/test/CodeGen/RISCV/rvv/variant-cc.ll
  llvm/test/MC/RISCV/directive-variant_cc-err.s
  llvm/test/MC/RISCV/directive-variant_cc.s
  llvm/test/tools/llvm-readobj/ELF/dynamic-tags-machine-specific.test
  llvm/test/tools/llvm-readobj/ELF/riscv-symbols-stother.test
  llvm/test/tools/obj2yaml/ELF/riscv-sym-other.yaml
  llvm/tools/llvm-readobj/ELFDumper.cpp

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